The mRNA for tissue plasminogen activator (t-PA) is present in primary mouse ooctyes but not translated. Upon meiotic maturation, this mRNA has 400-500 (A) residues added to the 3' end, begins to be translated, and is degraded. Using this system, and approaches developed to study t-PA mRNA recruitment, we propose the following: 1. To investigate using injection of RNA fragments and chimeric mRNAs the sequences in t-PA mRNA that determine its precise elongation, translational activation and subsequent degradation during oocyte maturation. 2. To search for molecules involved in oocyte maturation, meiosis and fertilization using cDNA libraries prepared from primary oocytes. 3. To assess whether information about meiosis gathered from other species, notably the fission yeast Schizosaccharomyces pombe and Xenopus laevis, can be used to further understand this process in mammals.